Method and system for identification of a center of a vertebral disc space and corresponding central axis of a spinal column

ABSTRACT

An apparatus for locating a central axis of a spinal column and method of using the same is disclosed. The apparatus and method includes one or more members capable of spanning a center line which may then be identified by at least one additional member positioned therebetween. Furthermore, the device may contain or be capable of accommodating various additional tools for marking the location of the central axis of a spinal column.

This application is a continuation of U.S. patent application Ser. No.13/023,279, filed on Feb. 8, 2011 (now U.S. Pat. No. 8,690,887), whichclaims the benefit of U.S. Provisional Patent Application Ser. No.61/302,357, filed on Feb. 8, 2010, the entire disclose of which ishereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates generally to a method and apparatus foruse in spinal surgery. More specifically, the present disclosure relatesto instruments for locating and marking points along a spinal vertebracolumn and/or along the anterior longitudinal ligament. Identificationof a center of a vertebral disc and corresponding central axis of aspinal column facilitates various procedures, such as disc arthroplasty.

BACKGROUND OF THE INVENTION

The human spinal column is generally divided into three sections: thecervical, thoracic, and lumbar spine. Portions of the spine, known asvertebrae, are divided by intervertebral discs. Due to a variety ofstresses and forces imparted upon the spinal column, damage tointervertebral discs is not uncommon. Conventional methods of treatingand repairing damaged discs include spinal arthrodesis (i.e. spinalfusion) and surgical replacement of a disc with an artificial disc (i.e.disc arthroplasty).

When performing these and other procedures, it may be important ornecessary to determine a specific location along the spinal column oramong the various vertebral bodies, such as the center axis of thespinal column, so that the surgeon may locate and/or mark control partsfor completing one of the various procedures conducted with referencethereto. Locating the center axis of a spine, however, may provedifficult given the variations in patient anatomy that may result from,for example, patient size, abnormalities of the spine and surroundingstructure, and an absence of typical anatomical landmarks. Otherproblems that contribute to the difficulty of locating markers in apatient include limited visibility due to the presence of tissue, blood,etc., or the lack of adequate lighting, or the presence of tools ordevices placed in the patient to complete the surgery. Locating markerswithin a patient during minimally invasive surgery may also be difficultdue to visual constraints.

Methods for identifying working points about a spinal column utilizingradiographic means are known in the art. For example, U.S. PatentApplication Publication No. 2007/0242869 to Luo et al., which is herebyincorporated by reference in its entirety, discloses a method foracquiring radiographic images of a spine and locating and calculatinggeometrical information, including the center line of the spine.However, images obtained by radiographic means may be of limited valuein determining a center axis of the spine, may require additionalexpenditure of time, expense, and effort to obtain such images,sometimes resulting in misidentification or miscorrelation of anatomicalfeatures and radiographic images, etc. Moreover, obstructions resultingfrom a patient's size and the potential presence/absence of anatomiclandmarks that are required to determine the center line by radiographicmapping create practical problems. The invention of Luo et al. andsimilar methods further subject the patient to radiation exposure whichmay be undesirable.

Various methods and devices which employ radiographic means suffer fromvarious drawbacks and complications. These include, for example, theneed to subject both a patient and a physician or user to radiation,time consuming preparation and administration of radiologic techniques,and the potential for inaccurate or inconclusive results due to thepresence of anatomical anomalies or absence of anatomical landmarks.

Therefore, there is a need for an instrument and method capable ofaccurately and repeatedly identifying one or more points along a spinalcolumn, such as a center axis of a spine. There is further need toeconomically and quickly, during a surgical procedure, determine thesepoints or “markers” without relying upon radiographic imaging and thatotherwise addresses the problems associated with prior art methods. Thefollowing disclosure describes an instrument that employs a novelcombination of features that address these long felt needs and furtherdescribes a method for using the same.

SUMMARY OF THE INVENTION

The present invention improves upon various known devices by providingan instrument that takes advantage of various features of the humanspine to identify, target, and/or mark the location of a center axis ofa spine. According to one embodiment, this instrument may further beused in minimally invasive procedures.

Various embodiments of the present invention, as described herein, relyupon certain anatomical consistencies in order to isolate, identify,target, and/or mark certain features or locations. For example, devicesof the present invention may be used in conjunction with a humanAnterior Longitudinal Ligament (“ALL”). The ALL is known to generallytraverse a longitudinal distance of a spine, with the center of the ALLin lateral alignment with a central axis of the spinal column. Devicesand features of the present invention may be used to identify and/ormeasure a center position of an ALL and thereby determine the centralaxis of a patient's spine. The present invention further contemplatesuse in identification of various other ligaments and regions of thehuman body to assist in various procedures.

U.S. Patent Application Publication No. 2009/0222011 to Lehuec et al.,which is hereby incorporated by reference in its entirety, discloses atargeting instrument for use in spinal disc replacement operations.Lehuec et al. discloses a device to be inserted between vertebralmembers of a patient and aligned with a mid-line of the spine. However,Lehuec et al. does not teach a method or apparatus capable of locatingthe mid-line without the use of radiographic imagining. Lehuec et al.further discloses a device that is not suited for minimally invasiveprocedures and which is more suited for procedures that are relativelytime consuming.

U.S. Patent Application Publication No. 2009/0270873 to Fabian, which ishereby incorporated by reference in its entirety, discloses a surgicalinserter for inserting an implant into a vertebral space. Portions ofsuch devices may be used in addition to in place of various componentsof the present invention. For example, in one embodiment, a grip andgrip activator may be used to measure and/or make contact with theperipheral boundaries of an ALL.

U.S. Patent Application Publication No. 2009/0299477 to Clayton et al.discloses a method and system for implantation of a device between twovertebral bodies using image guided surgical navigation, and is herebyincorporated by reference in its entirety. Clayton et al., however,fails to teach a device and method that does not require image sensingdevices to locate a central axis of the spine. Clayton et al. disclosesa device which contemplates the use of an image sensing device apartfrom human observation and a corresponding imaging display mechanism.Accordingly, Clayton et al. fails to teach several novel aspects of thepresent invention.

U.S. Patent Application Publication No. 2009/0304143 to Pakzaban, whichis hereby incorporated by reference in its entirety, discloses a deviceand method for non-invasively locating a spinal segment using laserdiodes and a method of marking a patient's skin with an estimatedlocation of a central axis with additional information provided by anX-ray source. Pakzaban discloses a device and method which requires theuse of radiologic imaging and that further does not provide for theability to mark portions of a spine and/or surrounding tissue with anindication of a central axis.

According to varying embodiments disclosed herein, the present inventionmay be comprised of a central body portion, hinged members, markingdevices, apertures to accommodate marking devices, adjustable fasteners,clamps, screws, etc., and members extending to various peripherallocations of an ALL. Embodiments of the present invention may be used,for example, in identifying a central axis of a spine with reference tothe ALL. In one embodiment, the present invention comprises extendingmembers for contacting both lateral peripheral boundaries of an ALL.Contact between extending members with both lateral peripheralboundaries of an ALL simultaneously positions at least a thirdmember/portion of the invention with a center line/point of the ALL,which corresponds with a center line/point of a spinal column.

In one embodiment, the present invention utilizes hinged or pivotingand/or extending members capable of accommodating various ALLs. Forexample, two or more hinged members may be employed to determine thelateral peripheries of an ALL and thereby determine a center line of theALL and spinal column based on the communication between the hingedmembers and a common axis of rotation. In another embodiment, thepresent invention may further include one or more additional means formarking or otherwise identifying the location of a central spinal axis.For example, a common axis of rotation of two hinged members may furtherinclude an aperture or means for accommodating a chisel or electrodedevice and thereby allow for the marking of the lateral positioning of acenter axis of a spine. Thus, in one embodiment, the present inventioncomprises a device for identification of a center of a vertebral discand corresponding central axis of a spinal column, further comprising:

a first and second member of substantially similar length/dimensionshaving first and second ends and hinged about a common axis;

the first and second members further comprising extending members withextend substantially perpendicularly to the first and second member;

a third member having a first end and a second end and hinged about anaxis generally perpendicular to the common axis; and

the second end of the third member representing a point equidistant fromthe second ends of the first and second members.

In an alternative embodiment, the present invention comprises a devicefor identification of a center of a vertebral disc and correspondingcentral axis of a spinal column, further comprising:

a first and second member of substantially similar length/dimensionshaving first and second ends and hinged about a common axis;

the first and second members extending from a main portion;

the center of the main portion being equidistant from the second ends ofthe first and second members; and

wherein the main portion further comprises an aperture useful forindicating, visualizing, and/or marking a point equidistant from thesecond ends of the first and second member.

In various embodiments, aspects of the present invention comprise ahandheld portion to facilitate user manipulation and use of the device.A single handheld portion, suited to fit in a surgeon's hand(s), isprovided that is in communication with various patient contactingportions of the present invention. For example, at least two extendingmembers may be in communication with a handheld/handle portion that arecapable of contracting or translating to identify the peripheralboundaries of an ALL or similar anatomical feature. A trigger mechanismcan be employed to permit the surgeon to depress a trigger and thuscause patient contacting elements to move in a predetermined fashionabout a patient's ALL boundaries. A third member, such as a markingdevice, a laser, an additional extending member, or other similar zoneand/or point identifying device may additionally extend or emanate fromthe handheld portion. Such embodiments allow a user to place a device ina desired position with relative ease and reduced risk of slippage ordropping of the device.

In another embodiment, once a user properly positions the device,features and methods of the present invention may be activated. Forexample, a dial, button, or similar actuating device may be provided ona handheld portion which allows a user to activate the contraction ofextending members or positional devices. Extending members mayadditionally comprise contact sensing elements that terminate thecontraction of extending members and/or provide feedback to a user thatcontact with an object (e.g. an ALL) has been made. Embodiments of thepresent invention may further include means for identifying and/ormarking a center line once this contraction or similar motion iscompleted. For example, once an object is identified by the previouslydescribed contraction, a user may activate a component within or inaddition to the handheld portion to generate a mark or indication of thelocation of a particular location, preferably a center line and/orpoint. In one embodiment, a button may be pressed to project a laser orlight upon a center line. Alternatively, a marking device such as aBovie® pen may be deployed from the handheld portion to mark a centerline. In alternative embodiments, handheld portions may include ports,apertures, slots, recesses, or similar features to accommodateadditional devices to be inserted through the handheld portion. Variousdevices and methods of the present invention may therefore be operatedor performed without the need to use two hands.

Embodiments comprising a handheld device may further comprise variouselements/features at the working end of the device that are useful fordetermining a centerline. For example, an arced measurement device (e.g.protractor) may be disposed proximal to a handheld portion of the devicethat is further capable of being positioned (e.g. proximal or adjacentto) with respect to an ALL or similar object. In various embodiments,the arced measurement device may be transparent or translucent to allowfor complete viewing of an ALL or similar object and its boundaries.Accordingly, symmetrical features of an arced measurement device may bealigned with lateral boundaries of an object such as an ALL, thusallowing for a corresponding point equidistant from the symmetricalfeatures to represent the centerline of an object. Such a device mayfurther include marking devices that correspond with the pointequidistant from the symmetrical features, and thus, certain embodimentsinclude at least two apertures through which a surgeon can extend a pinor other marking device therethrough to identify a particular point,e.g. a center-point or line. For example, a handheld portion of thedevice may comprise a trigger or actuator to deploy or actuatedevices/elements that may at least temporarily mark the measuredequidistant point.

Accordingly, in one embodiment, the present invention comprises anarcuate transparent device capable of measuring at least two points ofan object and indicating at least a third point that is equidistant fromthe at least two points of an object and that further comprises a handleor gripping portion. The device and method of use may further includemeans for visualizing and/or marking the third point.

Attachments to the handle may be reversibly associated therewith, thuspermitting disposable elements (e.g. the protractor unit, thedual-pronged movable arms, etc.) to be associated for particularsurgeries or procedures. For example, for small individuals, infants,etc. a one-sized handle grip for a surgeon can accommodate differentsized and/or configured working attachments.

In yet another embodiment, the present invention contemplates variousdeployable features which may be useful in identifying a center line,center plane, or center position between two points. For example, oncevarious features of the present invention are appropriately positionedon either side of an object, a device which is located equidistant tothese features may be depressed, ejected, or dispelled from the presentinvention. For example, a tack or marker capable of attaching oradhering to an object may reside at the center point of the presentinvention. Such a device, when properly positioned by additionalcomponents of the present invention, may be deployed so that it remains(e.g. for a time during surgical procedures and/or permanently) toindicate a center line/plane, and the remainder of the device removedfrom the work area. Deployable devices of the present invention maycomprise phosphorescent or luminescent materials. Embodiments of thepresent invention have uses in three-dimensional surgical procedures, asit is important therein to define a center point or plane for variouspurposes.

In yet another embodiment, devices of the present invention may measurea width of an object and determine and/or identify the presence of acenterline without requiring physical contact between the device and theobject. For example, a device may be provided that allows a user todirect or guide two points of light (e.g. lasers) to desired positions(e.g. the lateral boundaries of an ALL or similar object). Once this isaccomplished, the device can calculate the distance between these pointsand further produce, provide, emanate, etc. an additional mark orreference point indicating the position of a centerline. Embodiments ofthe present invention measure and/or identify a centerline throughpurely physical features and, in certain embodiments, incorporate logicto determine a centerline point and/or means for positioning a marker atthe centerline point.

Accordingly, devices of the present invention include a handheld portionin communication with extending members that do one of, and preferablyat least two of the following: measuring, identifying, and/or markingvarious features of an anatomical object, while leaving said devicesfree for manipulation by one hand of a user. Various features of U.S.Pat. No. 7,577,473 to Davis et al. and U.S. Pat. No. 7,637,917 toWhitfield et al., which are hereby incorporated by reference in theirentireties, may be incorporated into handheld features of the presentinvention. Those of skill in the art will recognize that various ALLmeasuring devices may be interchangeable between various handheldportions of the present invention as described herein.

In various embodiments, apertures, slots, and/or means for accommodatinga chisel or electrode device may include portions of the device whichcan accommodate, guide, or direct a device that is useful for marking apoint indicated by the device. Where various features described hereinare referred to as slots, tubes, or apertures, one of skill in the artwill understand that various other means that are capable of receivingadditional devices are within the scope and spirit of the presentinvention. For example, a central point of the present invention may belocated at the center of an annular portion which is sized toaccommodate known commercial devices, such as a Bovie® pen or variousknown chisels. Accordingly, known devices may be received by the annularportion in a manner that ensures marking at a central location of thedevice. Aspects of the present invention may further include, or providefor the reception of, marking devices which utilize radiographic ink,luminescent ink, bone scarring devices, and various other markingmethods. For example, various inks suitable for use within a surgicalcavity, including luminescent inks, may be applied to a portion of aspine or ALL. The application of these inks may be accomplished, atleast in part by, features of the present invention. Dyes such as thosedisclosed in U.S. Pat. No. 6,180,085 to Achilefu et al., which is herebyincorporated by reference in its entirety, may be employed. Inks anddyes suitable for use within a surgical workspace may consist of thosevisible to the naked eye as well as various dye and inks which requireadditional imaging or viewing means. Various embodiments may alsoinclude marking and other devices as described herein as a portion ofthe main body of the device (i.e. integrated within a portion of thedevice).

Various features of the present invention may be comprised oftranslucent or transparent materials which may reduce the amount ofvisual obstruction posed by a device. For example, one or more portionsof a device may be comprised of a plastic, Lucite, or other similartranslucent material which allows a user to visualize portions of aspine or similar feature that may be obstructed by opaque materials.Furthermore, devices and components may be disposed within transparentor translucent materials to further aid in visualization and targetingof certain objects. In one embodiment, cross-hairs or similar targetingfeatures may be employed within or proximal to features of the presentinvention. Where translucent features are incorporated into theinvention, these targeting features may be disposed within translucentfeatures and help identify, guide, or target various other devices andprocedures.

Materials and devices may also be employed that act to aid invisualization. Magnifying lenses may be incorporated into variousfeatures of the present invention. For example, various known lenses maybe placed over an aperture or slotted portion in order to magnify andprovide greater visualization of a workspace, including, by way ofexample and not limitation, a center point of an ALL.

Various projection means may be incorporated into embodiments of thepresent invention. For example, known methods of projecting lasersand/or similar markers, such as those described in U.S. Pat. No.6,914,930 to Raskin et al. for a laser level, may be used to project apoint or line along an axis that has been identified as describedherein.

Various features of the present invention may also be illuminated.Illumination means, such as LED lights and similar devices may beemployed in various different positions on disclosed embodiments. Forexample, an LED may be positioned at a central point of the presentinvention in order to cast light into a surgical work area. Lightingmeans may also be employed at the distal ends of various members toassist in visualization of the members and member extremities whenworking within a dark, crowded, and/or obstructed area. Lighting meansmay include, for example, various “glow in the dark” or phosphorescentmaterials. Various features of the present invention may be composed ofor coated with known phosphorescent materials.

Apertures, slots, compartments, and/or means for accepting a markingdevice may further be capable of accommodating various cannulas forminimally invasive surgical procedures. Cannula devices suitable forspinal surgery, such as those disclosed in U.S. Patent ApplicationPublication No. 2003/0083688 to Simonson and various other devices knownin the art may be employed within various features of the presentinvention. In one embodiment, apertures, slots, passages, etc. adaptedto receive a cannula have at least edge regions comprising a materialdistinct from the remainder of the device, including transparent aspectsand/or flexible or malleable regions that facilitate ease of positioningby a surgeon.

Embodiments of the present invention may further include the ability toadjust the length of one more members. Providing for adjustability ofvarious members may allow for a single device to accommodate a widearray of patients who may vary in size and various correspondingdimensions (e.g. depth to a spinal column, lengths of various portionsof the spinal column, etc.). As described herein, adjustability abouttwo or three distinct axis is preferred to permit surgeons to makeminimal adjustments to accommodate surgical situations that arise. Thus,nested or telescoping members, preferably having at least one flexiblecomponent, provide a surgeon with the ability to address the desiredpositional orientation of instruments as they relate to a patient'sphysical features.

In various embodiments, aspects of the present invention may comprisedisposable devices. In one embodiment, the entirety of a device may beformed from one or more relatively inexpensive materials which enabledevices to be discarded and replaced after each use, thus avoidingautoclaving and other sterilization procedures. In an alternativeembodiment, specific portions of the present invention may be detachablefrom a remainder of the device and discarded after use. By way ofexample only, extending members as will be described may be removablefrom a main portion of the device, disposable, and/or comprised of amaterial that provides for relative ease of replacement. Devices of thepresent invention may be comprised, at least in part, of polyether etherketone (or PEEK).

In alternative embodiments, the present invention incorporates reusablecomponents, such as surgical grade metals and plastics which may beautoclaved or similarly cleaned and sanitized for reuse in subsequentprocedures.

The present invention may additionally interface with various externaldisplay units and/or devices. U.S. Pat. No. 7,558,617 to Vilsmeier,which is hereby incorporated by reference in its entirety, discloses aneuro-navigation system comprising reflector referencing devices and amarker system for mapping various aspects of a patient. The presentinvention may, for example, interface with various different devicessuch as a surgical microscope, an ultrasonic diagnostic system, computeraided remote surgical operation systems, and/or various other devices.In yet another embodiment, the present invention includes a method whichfurther contemplates the use of various nerve testing devices, such asthose disclosed in U.S. Patent Application Publication No. 2010/0010367to Foley et al. which is hereby incorporated by reference in itsentirety.

In various embodiments, the present invention is employed in conjunctionwith various known imagining devices and serves as a supplemental orverification technique for determining the physical positions of variousanatomical structures. For example, when various known radiologicaldevices are used to map or determine the locations of various featuresor anatomical structures, embodiments of the present invention furtheroperate to confirm, evaluate, verify, etc. the information obtained fromsuch radiological devices. Similarly, embodiments of the presentinvention are alternatively used to acquire preliminary data on thelocation of anatomical features which are later confirmed or evaluatedby radiological and other similar imaging devices and procedures.Various visualization methods and devices which may be used inconjunction with the present invention include, for example, thosedescribed in U.S. Patent Application Publication No. 2009/0259123 toNavab et al., which is hereby incorporated by reference in its entirety.

In yet another embodiment of the present invention, various devices,such as touch-sensors or proximity sensors, may be provided in order todetect when certain portions of the present invention are proximate toor have made contact with, for example, an ALL. The device may furtherprovide feedback to a user based on the information received from suchdevices. For example, an LED light may indicate that contact with an ALLhas been made and that no further contraction of the present inventionis required.

In yet another embodiment, the present invention further incorporatesvarious means for measuring additional dimensions of a disc space. Forexample, devices similar to those disclosed in U.S. Patent ApplicationPublication No. 2010/0010494 to Quirno, which describes a method anddevice for determining an optimal size of an intervertebral implant tobe inserted within an intervertebral space and is hereby incorporated byreference in its entirety, may be incorporated into embodiments of thepresent invention.

Methods of determining the location of a disc space center axis,including methods further requiring preparation (e.g. cleaning, marking,etc.) of an ALL and similar anatomical structures are furthercontemplated by the present invention. For example, as one object of thepresent invention is to utilize an ALL as an anatomical landmark, amethod includes an ALL (or similar object) first being prepared ortreated before employing additional features of the present invention.An ALL or similar object may be cleaned and/or marked with various inks,dyes, or fixed objects such as staples, sutures, or other devices whichfacilitate the visualization of the lateral boundaries of an ALL orsimilar object. Additionally, conductive elements may be placed on,within, or proximal to an ALL in order to assist in proximity sensingoperations. For example, conductive materials, such as metallic elementsmay be placed at a boundary of an object such that additional contactsensing means disposed on other components of the present inventiondetect lateral boundaries. One embodiment, for instance includes thefollowing elements:

a) creating an access opening in a patient adjacent the patient's spine;

b) providing a center-locating tool adapted to fit within the accessopening, said tool comprising:

-   -   i) a handle portion; and    -   ii) a center-line indicating portion operatively associated with        said handle portion, said center-line indicating portion having        a first component for identifying one border of the patient's        ALL and a second component for identifying a separate border of        the patient's anterior longitudinal ligament, and a third        component for marking a point equidistant from each of said        borders;

c) inserting said center-locating tool into the access opening;

d) aligning said first component of said center-line portion with oneborder of a patient's ALL;

e) aligning said second component of said center-line portion with aseparate border of a patient's ALL;

f) marking a point equidistant between said borders using said thirdcomponent; and

g) removing the center-locating tool from said access opening after saidmarking step.

Although the description of various embodiments herein relates to theuse of a device within a surgical workspace, it will be recognized thatembodiments of the present may be utilized wherein at least portions ofthe device are external to a patient's body or a surgical work area. Theinvention may be utilized completely external to a patient's body,partially external to a patient's body, generally disposed within asurgical area, or completely disposed within a work area. Where devicesare to be used at least partially external a patient's body, additionalmarking devices may be utilized. U.S. Pat. No. 6,805,669 to Swanbom,discloses a method and device for marking skin during an ultrasoundexamination and is hereby incorporated by reference in its entirety.These and similar techniques and/or devices may be utilized when it isdesirable to mark an area external to a surgical cavity. Various imagingdevices, such as U.S. Pat. No. 6,982,740 to Adair et al., which ishereby incorporated by reference in its entirety, may be utilized withthe present invention, such as to provide illumination sources forhandheld embodiments.

These and other advantages will be apparent from the disclosure of theinvention(s) contained herein. The above-described embodiments,objectives, and configurations are neither complete nor exhaustive. Aswill be appreciated, other embodiments of the invention are possibleusing, alone or in combination, one or more of the features set forthabove or described in detail below. Further, this Summary is neitherintended nor should it be construed as being representative of the fullextent and scope of the present invention. The present invention is setforth in various levels of detail in this Summary, as well as in theattached drawings and the detailed description below, and no limitationas to the scope of the present invention is intended to either theinclusion or non-inclusion of elements, components, etc. in thisSummary. Additional aspects of the present invention will become morereadily apparent from the detailed description, particularly when takentogether with the drawings, and the exemplary claim provided herein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is top plan view of an instrument for locating one or more pointsabout a spinal column according to one embodiment;

FIG. 2 is a side perspective view of the instrument of FIG. 1;

FIG. 3 is a side perspective view of device for identification of acenter of a spinal column according to one embodiment;

FIG. 4A is a perspective view of a device for identification of a centerof a spinal column according to one embodiment;

FIG. 4B is a perspective view of a device for identification of a centerof a spinal column according to one embodiment;

FIG. 5 is a perspective view of yet another device for identification ofa center of a spinal column according to one embodiment;

FIG. 6 is a perspective view of yet another device for identification ofa center of a spinal column according to one embodiment;

FIG. 7 is a perspective view of yet another device for identification ofa center of a spinal column according to one embodiment;

FIG. 8 is a perspective view of a device for identification of a centerof a spinal column according to one embodiment;

The drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE FIGURES

Referring now to FIGS. 1 and 2, a disc space centering tool according toone embodiment of the present invention is shown. The tool 10 is shownwith reference to an ALL 14. The ALL 14 is known to generally span thelongitudinal length of an anterior portion of the human spine and alignwith a central axis of rotation of the spine. Accordingly, the ALL 14generally provides a useful reference point for measuring, tracking, orotherwise identifying a central axis of a spine for surgical procedures.

In one embodiment, the device 10 includes two or more hinged or movablemembers 18 a, 18 b useful for identifying the lateral boundaries of anALL 14. Hinged members of the present invention may further includeperpendicularly extending members 42 a, 42 b that facilitate in thedetermination of a width of an ALL 14. For example, perpendicularlyextending members 42 a, 42 b may be comprised of pins or similarextensions that provide for a contact point(s) with the device 10 and anALL 14.

As one of ordinary skill in the art will recognize, visibility within asurgical workspace may often be obstructed by various tissues andfluids. Accordingly, a clear view of an ALL 14 may not be available. Inorder to account for this, members 42 a, 42 b of the present inventionprovide a means whereby the boundaries of an ALL 14 may be determinedthrough tactile as well as visual feedback, and further via electronicsensing means, such as those employing proximity sensors or computeraided systems (not shown).

In one embodiment, portions of extending members 42 a, 42 b compriseadditional means for sensing the proximity of an ALL 14. For example,various known tactile pressure sensors may be implemented in extendingmembers 42 a, 42 b that provide indication of contact between anextending member 42 and an ALL 14. Accordingly, a signal correspondingto this contact may be displayed to a user, either on a portion of thedevice 10 or as part of an external display unit.

Extending members 42 a, 42 b may be of unitary construction with hingedmembers 18 a, 18 b or may be non-fixedly attached to hinged members 18a, 18 b and selectively adjustable in various degrees of freedom. Forexample, extending members 42 a, 42 b may be constructed or positionedthrough hinged members 18 a, 18 b and may further comprise a round orflat head rivet 30, 34 or similar means to prevent undesired movement.Additionally, the device 10 may further comprise means for fixing one ormore extending members 42 a, 42 b in a variety of positions. Forexample, means for fixing an extending member 42 a, 42 b may comprise aset screw 38 and a slot 36 which allow for positioning of an extendingmember 42 a, 42 b in one or more axis. For example, a slot 36 mayprovide for the ability to position an extending member 42 a, 42 b in anon-discrete number of longitudinal and vertical positions. A set screw38 may further be provided to affix an extending member 42 a, 42 b in adesired location.

In one embodiment, extending members 42 a, 42 b may be spring loadedretracting members, capable of retracting within themselves and/orthrough various portions of the device (e.g. hinged members 18 a, 18 b).Extending members 42 a, 42 b may also be coated or comprised of variousphosphorescent materials and/or filled with various materials. Forexample, one embodiment contemplates filling extending members 42 a, 42b with ink or dye which may be selectively deployed to mark locations.In an alternative embodiment, extending members 42 a, 42 b are filledwith a phosphorescent material to further aid in visualization andlocation of various objects, such as an ALL 14.

It will be recognized that certain embodiments of the present invention10 may require distal points of extending members 42 a, 42 b to residein a generally co-planar manner in order to dictate that a centralmember 24 further resides on a center line of an ALL 14 or similarobject. Accordingly, it may be undesirable to adjust a single extendingmember 42 a, 42 b without similarly adjusting the second or additionalextending member(s). Therefore, in one embodiment of the presentinvention, extending members 42 a, 42 b may be in fixed communicationwith each other such that the distal adjustment of one is physicallydependent upon the same magnitude of adjustment of the other. Forexample, extending members 42 a, 42 b may be joined or fused togetherwith an additional member which prevents the vertical displacement ofone member without the other.

Two or more hinged members 18 a, 18 b may be joined to a central member24 such that hinged members share a common axis of rotation.Accordingly, when one or more of the hinged members 18 a, 18 b isrotated about its hinge, the longitudinal axes of the hinged members 18a, 18 b and a line bisecting two hinged members 18 a, 18 b willintersect at a common point within a central member 24. Accordingly, byplacing extending members 42 a, 42 b of the present invention 10 at thelateral boundaries of an ALL 14, the center line of an ALL 14 may beidentified by the resulting position of the attached central member 24.Those of skill in the art will further recognize that the center line ofan ALL 14 will correspond to the disc space center line of a patientwithin a reasonable degree of certainty in most applications.

In one embodiment, a central member 24 of the present invention 10further comprises means for marking or targeting a center line position.For example, central member 24 may comprise an aperture, tubular member,or other similar member 22 capable of receiving an additional device,which provides for direct visualization and/or access to a spinal/ALLcenter line. Aperture 22 may accommodate various additional devices,such as surgical tools useful for marking a center line or devices forconducting various surgical procedures within a central member 24. Oneof skill in the art will recognize various devices useful for marking aposition or center line as indicated by the present invention. Forexample, various chisels and electrodes may be employed to create aphysical mark on a portion of a patient's ALL 14 or vertebral disc at alocation identified by the present invention as described herein.Alternatively, a laser or light may be positioned to correspond with acenter line position as identified by the present invention. Such adevice may provide, for example, a non-injurious indication of a discspace axis while disposed within a surgical work space or after thepresent invention has been removed from a work space.

Alternatively, a central member 24 may comprise a tubular member 22 orother sufficiently large aperture within which various procedures may beconducted. For example, once a center line has been identified accordingto various embodiments of the present invention, the tubular member oraperture 22 of the device 10 may provide a sufficient workspace withinwhich surgical tools and devices may be accommodated and a user mayperform various tasks.

In one embodiment, a disc space centering tool 10 comprises a screw 46in communication with the plurality of hinged members 18 a, 18 b forsetting and/or maintaining a precise relative position of hinged members18 a, 18 b. Such a screw 46 comprises a thumbscrew threaded through onehinged member 18 b and at least partially threaded through anotherhinged member 18 a. By adjusting the position of the screw 46, a desiredangular displacement between hinged members 18 a, 18 b may beestablished and maintained.

A method of use for the previously described device is contemplatedwhereby hinged members 18 a, 18 b and a central member 24 may be used tolocate and/or identify a central axis of a spinal column. According toone embodiment, hinged members 18 a, 18 b may be expanded to a desiredwidth and generally situated so that hinged members 18 a, 18 b arepositioned on either lateral boundary of an ALL 14. Once hinged members18 a, 18 b are generally situated on either side of an ALL, hingedmembers 18 a, 18 b may be contracted to a position where both hingedmembers 18 a, 18 b contact the lateral boundaries of the ALL 14. In oneembodiment, a user may determine the existence of contact betweenaspects of the present invention and an ALL 14 through visualobservation and/or tactile sensation. In another embodiment, thepresence of this contact may be communicated to a user by varioussensing means. For example, touch-sensors or similar devices may beimplemented into a distal portion of hinged members 18 a, 18 b that arecapable of determining contact between the present invention 10 and anALL 14. In one embodiment, upon contact with an ALL, touch-sensors ofthe present invention provide feedback to a user, such as through visuallight indicators or audio indicators, that contact has been made and nofurther contraction of hinged members 18 a, 18 b is required.

Once the hinged members 18 a, 18 b have been brought into contact withan ALL 14 or other object whose center line is to be determined, centralmember 24 may then be used for identifying, targeting, and/or marking acenter line of the object identified by hinged members 18 a, 18 b aspreviously described. Marking of this center point may be accomplished,by example, through a variety of tools, methods and devices, including,but not limited to, Bovie® pens, chisels, tamping devices, and/orvarious inks or dyes.

Once a center line has been identified as previously described, it maybe marked by various different methods and devices. In one embodiment,central member 24 further comprises means for marking an ALL 14 orobject whose center line is to be located. For example, a central member24 comprises an electrode containing device capable of marking a pointrepresentative of a spinal center line. Accordingly, once the device 10is properly positioned, a user may activate features of such a device tocauterize or mark a point which is to serve as a visual indicator of acenter line for the remainder of surgical procedures to be performed. Inone embodiment, central member 24 may include an aperture or tubularmember 22 through its center capable of accommodating various devicesuseful for marking a point, such as a Bovie® pen or similar electrodecontaining device, chisel, or other marking device. In this embodiment,a center line may be marked or indicated by inserting the appropriatedevice within aperture 22 and performing the appropriate function (e.g.activating the electrode pen or tamping down a chisel to provide amark).

According to various embodiments, once a center line has been determinedand the appropriate mark or indication made, the device 10 may beremoved from the work area. It will be recognized, however, that thedevice 10 may be left within a surgical workspace and continue to serveas a reference point for a center line. For example, where proceduresare to be conducted which do not require the level of access and freedomof movement provided by the removal of the device 10, the device 10 mayremain within the workspace as a physical indicator of a center line.

It will be recognized that the present invention 10 may be used toidentify additional reference points (i.e. those other than a pointcorresponding to a spinal central axis). For example, once the center ofan ALL is determined, the device 10 may be translated to anotherposition without adjusting the angular position of hinged members 18a,b. By doing so, additional points may be identified or marked. Thesepoints may, for example, constitute points of equal distance away from acentral axis and provide additional reference points in the event thatone or more points becomes obstructed from view or simply where it isadvantageous to have a plurality of reference points with which to alignvarious objects.

Various embodiments of the present invention further comprise theability to enable or assist in minimally invasive surgical procedures.For example, a central member 22 of the present invention may beconstructed in a manner that allows the device 10 to receive variouscannulas and/or minimally invasive surgical devices known to those ofskill in the art. In alternative embodiments, aspects of the presentinvention may be combined or affixed to currently known minimallyinvasive devices, such as those disclosed in Applicant's U.S.Provisional Patent Application 61/120,260, which is hereby incorporatedby reference in its entirety.

FIG. 3 is a side perspective view of a disc space centering toolaccording to one embodiment of the present invention. As shown, hingedmembers 18 a, 18 b share a common axis of rotation and are hinged sothat members 18 a, 18 b are always an equal angular displacement awayfrom a center-line bisecting the two members 18 a, 18 b. Accordingly,hinged members 18 a, 18 b span and identify the width of a given space,such as an ALL 14, and identify a centerline of the space that isdisposed midway between the hinged members 18 a, 18 b. The device mayfurther include an additional member 50 for identifying a spinal centerline. In one embodiment, indicating member 50 is free to rotate about asingle axis, where that axis may be perpendicular to the axis ofrotation of the other hinged members 18 a, 18 b. Indicating member 50may therefore be a pivotable extension of the bisecting line betweenhinged members 18 a, 18 b and thus useful for marking or otherwiseindicating the midline of an ALL and corresponding spinal midline. Inalternative embodiments, one or more of the extending members 50, 18 a,18 b are fixedly attached to a connecting portion 58.

It will be recognized that in various spinal procedures, the height ofvertebrae 62 and vertebral discs 66, and the different longitudinaldistances d that embodiments of the present invention will need to spanwill be based on patient size and the portion of the spine upon whichprocedures are to be performed. Accordingly, indicating member 50 may behingedly attached to a connecting portion 58 by a joint 54 which allowsfor different distances d to be established. It will also be recognizedthat similar adjustability may be achieved by providing for extendableor telescoping members 18 a,b as shown and described with respect toFIG. 1.

In one embodiment, the device 10 may further include a thumbscrew (46 inFIG. 1) or similar adjustable member useful for adjusting and orsecuring the rotational position of hinged members 18 a, 18 b. Inanother embodiment, a plurality of indicating members 50 are provided.In yet another embodiment, indicating member 50 may comprise telescopiccapabilities such that indicating member 50 is free to expand orcontract along its own axis and provide additional functionality formarking a point at a distance d away from hinged members 18 a, 18 b.

Various hinged members of the present invention may be biased orincorporate springs. As used herein, biased may refers to both a linearand non-linear bias or spring force. For example, hinged members 18 a,18 b may include one or more springs (e.g. a coil spring extending intoboth members 18 a, 18 b) which may bias the movement of the members. Inone embodiment, a biasing force may be sufficient to retract hingedmembers 18 a, 18 b toward each other at least to an extent that they donot compress an object disposed within the members (e.g. an ALL 14).

Various lighting means and/or mechanisms are further contemplated by thepresent invention. LED lighting may be provided, for example, at anintersection of members or provided as an extension or attachment to thepresent invention. It will be recognized that various lighting devicesmay serve to illuminate a surgical space, particularly where thesurgical space is small, dark, and/or obstructed. Lighting means, suchas LED lights or fiber-optic lighting may be employed at a distal end ofone or more hinged members or at various other points on a device. Suchdevices are employed to generally illuminate an area and/or to provide auser with additional clarity and visibility as to the distal portions ofvarious features of the present invention.

It is further contemplated that various portions of the presentinvention may be comprised of generally disposable materials. Theentirety or portions of embodiments of the present invention may becomprised of materials generally known to be relatively inexpensive andcapable of being discarded after even a single use. For example, members18 a,b, 50 may be comprised of a detachable portion that is discardedafter use and replaced with another item of the same or similarconstruction.

As shown in FIGS. 4A-4B, various embodiments of the present inventionmay be disposed upon devices suitable for use with only hand of theuser. In one embodiment, hinged members 18 a, 18 b, 82A, 82B and one ormore hinges 106 are provided. Hinged members may be operated via switch110 which is capable of contracting and/or expanding hinged member 18 a,18 b, 82A, 82B. Marking member 50 is further provided to indicate acenterline as measured by hinged members 18 a, 18 b. Features of markingmember 50 may be selectively controlled by a trigger or activationdevice 74. In various embodiments, these features comprise light orlaser emitters, Bovie® pens, and various other similar marking devices.

FIGS. 5-6 depict alternative embodiments of the present invention. FIG.5 depicts an embodiment wherein a measuring device 78 is disposed on thedistal end of a handheld portion 70. In one embodiment, the measuringdevice 78 comprises a translucent arced member which allows forvisualization of an ALL through the device. By aligning the peripheralboundaries of an ALL on either side of a central portion 102 of thedevice, a center line of an ALL and associated central axis of a spinalcolumn may be indicated by various components of the present invention,such as indicia 98. In one embodiment, the device further comprises anactivator device 74 which activates a marking device. Marking devices ofthe present invention may include, for example, light or laser emitters,chisels, Bovie® pens, and similar tools.

FIGS. 6-7 depict embodiments wherein a handheld portion 70 is providedto allow a user to easily grip the device 10. Extending member 82A, 82Bare provided with perpendicular extending member 86A, 86B capable ofdetermining the peripheral boundaries of an ALL. In one embodiment,members 82A, 82B are hinged and controlled by a user such that they maybe contracted (e.g. by a push button) without requiring the use of twohands. In one embodiment, the invention further comprises a markingdevice 90, such a laser emitting device which projects a line or point94. For example, once the device 10 and members 82A, 82B areappropriately positioned, a trigger member 74 may be activated toproject a laser line and/or point. Those of skill in the art willrecognize that various handheld portions 70 as shown and described maybe used in conjunction with various different ALL measuring/centeringdevices as described herein. Thus, the present invention is not limitedto any specific combination or arrangement of the novel devices shownand described herein.

Accordingly, a method of use of the present invention is providedwherein a disc space centering tool may be employed within a surgicalworkspace to identify a center or midline of a spinal column. In discarthroplasty procedures, it is desirable to place a replacement disc asclose to the center of a rotational axis of the spine as possible. Atolerance of 3 mm of displacement between the central axis of the spineand the center of an implanted artificial disc is preferred, althoughtighter tolerance is typically desired. In one embodiment, hingedmembers 18 a, 18 b may be expanded to a desired width and generallysituated so that hinged members 18 a, 18 b are positioned on either sideof an ALL 14. Concurrently, an indicating member 50 may be rotatedupward so that it does not impair movement or visibility of the device10. Once hinged members 18 a, 18 b are generally situated on either sideof an ALL 14, hinged members 18 a, 18 b may be contracted to a positionwhere both hinged members 18 a, 18 b contact the lateral boundaries ofthe ALL 14.

In one embodiment, a user may determine the existence of contact betweenaspects of the present invention and an ALL 14 through visualobservation and/or tactile sensation. In another embodiment, thepresence of this contact may be communicated to a user by varioussensing means. For example, touch-sensors or similar devices may beimplemented into a distal portion of hinged members 18 a, 18 b that arecapable of determining contact between the present invention and an ALL14. Upon contact with an ALL 14, touch-sensors of the present inventionmay provide feedback to a user, such as through visual light indicatorsor audio indicators, that contact has been made and no furthercontraction of hinged members 18 a, 18 b is required.

Once the hinged members 18 a, 18 b have been brought into contact withan ALL 14 or other object whose center line is to be determined,indicating member 50 may then be useful for identifying, targeting,and/or marking a center line of the object identified by hinged members18 a, 18 b as previously described. Those of skill in the art willrecognize that that longitudinal position of indicating member 50 willvary as a function of its rotational positional about an axis z, therotation or tilt of the device 10, and the lengths of the hinged members18 a, 18 b and indicating member 50. Accordingly, various spans ordistances d between a distal point of hinged members 18 a, 18 b andindicating member 50 may be achieved. Those of skill in the art willrecognize the inherent utility in this feature as different distances dwill be desired based on variations in patient size and portion of thespine under consideration.

Once a center line has been identified as previously described, it maybe marked by various different methods and devices. In one embodiment,indicating member 50 further comprises means for marking an ALL 14 orobject whose center line is to be located. For example, the distal endof an indicating member 50 may comprise an electrode containing devicecapable of marking a point representative of a spinal center line.Accordingly, once the device 10 is properly positioned, a user mayactivate the features of such a device to cauterize or mark a pointwhich is to serve as a visual indicator of a center line for theremainder of surgical procedures to be performed. In one embodiment,indicating member 50 may include a through-hole through its centercapable of accommodating various devices useful for marking a point,such as a Bovie® pen or similar electrode containing device, chisel, orother marking device. In this embodiment, a center line may be marked orindicated by inserting the appropriate device within indicating member50 and performing the appropriate function (e.g. activating theelectrode pen or tamping down a chisel to provide a mark). A spinalcenter line or other location may also be marked using various dyes andinks as described herein. Once procedures are completed, variouscomponents as described herein may be discarded or properly sanitizedfor reuse.

According to various embodiments, once a center line has been determinedand the appropriate mark or indication made, the device 10 may beremoved from the work area. It will be recognized, however, that thedevice 10 may be left within a surgical workspace and continue to serveas a reference point for a center line. For example, where proceduresare to be conducted which do not require the level of access and freedomof movement provided by the removal of the device 10, the device 10 mayremain within the workspace as a physical indicator of a center line.

In another embodiment, a center line may be marked by rotating thedevice 10 and an indicating member 50 in a substantially simultaneousmanner. It will be recognized that when an indicating member 50 is incontact with an ALL 14 or other object, rotating the indicating memberalone about an axis z will either result in merely applying force to theobject 14 or rotation of the indicating member 50 away from the object14. However, it will also be recognized that where the indicating member50 and the object 10 itself are rotated generally simultaneously,contact between a distal end of an indicating member 50 and an object 14may be preserved while the distal end of an indicating member 50translates along a length of the object 14. In this manner and inconjunction with marking devices and methods as previously described, acenter line of an ALL 14 or similar object may be marked by a singlepoint, a plurality of points, or a continuous line.

FIG. 8 depicts another embodiment of the present invention wherein adevice 10 is provided with at least one fixedly attached member 200. Asshown, an indicating member 200 is provided wherein the indicatingmember is fixedly attached to a connecting portion 206 and additionalmembers 202 a, 202 b are hingedly attached and rotatable about a commonpoint. A fixedly attached member 200 may be secured to or incommunication with a connection portion 206 via any number of knowndevices or methods including, but not limited to, press-fitting,tack-welding, bonding, various adhesives, etc. In one embodiment, anadjustment device 208 is provided for adjusting the position of at leasthinged members 202A, 202B. Adjustment device 208 is further adapted foruse in manipulating or controlling the device 10. In one embodiment,member 208 does not comprise an adjustable portion, but rather isprovided so a user may grasp the device 10 at a user-proximal portion.In one embodiment, at least one member of the device 10 comprisestelescoping features and/or marking features as shown and describedherein.

While various embodiments the present invention have been described indetail, it is apparent that modifications and alterations of thoseembodiments will occur to those skilled in the art. However, it is to beexpressly understood that such modifications and alterations are withinthe scope and spirit of the present invention, as set forth in thefollowing claims. Further, the invention(s) described herein are capableof other embodiments and of being practiced or of being carried out invarious ways. In addition, it is to be understood that the phraseologyand terminology used herein is for the purposes of description andshould not be regarded as limiting. The use of “including,”“comprising,” or “adding” and variations thereof herein are meant toencompass the items listed thereafter and equivalents thereof, as wellas, additional items.

What is claimed is:
 1. A device for identification of a center of avertebral disc space and corresponding central axis of a spinal columncomprising: a) a single grasping portion at a user proximal end of saiddevice configured to facilitate a surgeon's manipulation and use of thedevice, said grasping portion comprising a single handheld extensionsuited to fit in a surgeon's hand when gripped by a surgeon, therebyfacilitating operation of said device without the need to use two hands;b) a center-line indicating portion operatively associated with saidsingle grasping portion, said center-line indicating portion having afirst component for identifying one border of the patient's anteriorlongitudinal ligament and a second component for identifying a separateborder of the patient's anterior longitudinal ligament, and a thirdcomponent for marking a point equidistant from each of said borders,said third component having an annular portion sized to accommodate acommercial device selected from the group consisting of a Bovie® pen, alaser emitter and an electrode device, said commercial device receivedby the annular portion in a manner that facilitates location of acentral location between said first and second components and togenerate an indication of the location of a particular location, c) aconnecting portion associated with the grasping portion, said connectingportion hingedly attached to said first component and said secondcomponent, said first component and said second component beingrotatable about a common point, each of said first and second componentshaving an extended longitudinal axis, with a first end associated withsaid connecting portion and a second end having a pointedpatient-contacting end extending directly in line with said axis; and d)an adjustment device for adjusting a position of one of the hingedlyattached first component and said second component, wherein said thirdcomponent is positioned between said first and second components whensaid first component, second component and third component are adaptedto be in contact with a patient's vertical disc space when identifying acenter of a vertebral disc space.
 2. The device as set forth in claim 1,wherein said device is disposable and said first and second componentscomprise PEEK.
 3. The device as set forth in claim 1, wherein saiddevice further comprises a set screw and a slot in communication withsaid components to maintain said components in a predetermined position.4. The device as set forth in claim 1, wherein said first component iscomprised of a phosphorescent material.
 5. The device as set forth inclaim 1, wherein said device comprises disposable components.
 6. Thedevice as set forth in claim 1, wherein said first and second componentscomprise PEEK.
 7. The device as set forth in claim 1, wherein said firstcomponent and said second component have similar length and dimensions.8. The device as set forth in claim 1, further comprising a triggermechanism employed to permit a surgeon to depress a trigger and move thefirst and second components.
 9. The device as set forth in claim 1,wherein said grasping portion includes a button or dial.
 10. The deviceas set forth in claim 1, wherein at least one of said first componentand second component comprise a proximity sensor.
 11. The device as setforth in claim 1, wherein said grasping portion includes an actuatorthat activates said commercial device to make a temporary mark at ameasured equidistant point.
 12. The device as set forth in claim 1,wherein said device comprises a translucent material.
 13. The device asset forth in claim 1, wherein said device further comprises a magnifyinglens positioned to provide visualization of a surgical work space. 14.The device as set forth in claim 1, wherein said device furthercomprises a source of illumination.
 15. The device as set forth in claim1, wherein one of said first and second components comprises atelescoping member.
 16. The device as set forth in claim 1, wherein saiddevice is configured to operably interfaces with one of a surgicalmicroscope, a computer aided remote surgical operation system and anultrasonic diagnostic system.
 17. The device as set forth in claim 1,further comprising an activator device comprising a laser.